Structures of three MFS proteins in alternate conformations were compared to identify residues involved in contacts in both states at the hinge points connecting the two six-TM domains. The proteins compared were LacY or lactose permease, the xylose transporter XylE, and the glucose transporter GLUT5 from rat (Protein Data Bank accession no. 4YBQ) and bovine (Protein Data Bank accession no. 4YB9). YajR, the template for the most recent VMAT2 models, is included for reference.